Photothermographic element comprising improved base precursors and methods for their use

ABSTRACT

Photothermographic elements employing improved base precursors that undergo thermal decomposition are disclosed. Thermal-dye-bleach agents, and in particular, a novel class of salts of arylsulfonylacetic acids as bleaching agents for photothermographic use are disclosed. Photothermographic elements employing these thermal-dye-bleach agents are suitable for use as acutance and antihalation systems, bleachable filter dye materials, and in promoting unblocking of various components such as blocked developers, especially in photothermographic elements.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a divisional of application Ser. No. 10/300,552, filed Nov. 20,2002 now U.S. Pat. No. 6,699,651.

FIELD OF THE INVENTION

This invention relates to improved thermal base precursors. Suchcompounds can be used, for example, in thermally bleachable filter dyecompositions or in other components in photothermographic elements.

BACKGROUND OF THE INVENTION

A thermal base precursor is a neutral or weakly basic compound which cangenerate a strong base during thermal processing. Various baseprecursors are known as, for example, described in U.S. Pat. Nos.3,220,846; 4,060,420 and 4,731,321. Japanese Patent Application No.1-150575 describes thermally-releasable bis-amines in the form of theirbis(aryl sulfonylacetic acid)salts. Other amine-generating compoundsinclude 2-carboxycarboxamide derivatives disclosed in U.S. Pat. No.4,088,469, hydroxime carbamates disclosed in U.S. Pat. No. 4,511,650 andaldoxime carbamates disclosed in U.S. Pat. No. 4,499,180. Examples ofsome thermal base precursors are shown in Table III of U.S. Pat. No.5,258,274 to Helland et al., including cations and anions, which patentis incorporated by reference.

Further examples of base precursors include salts of carboxylic acidsand organic bases as described in U.S. Pat. No. 3,493,374 (triazinecompounds and carboxylic acids), British Patent 998,949 (trichloroaceticacid salts), U.S. Pat. No. 4,060,420 (sulfonylacetic acid salts),JP-A-59-168441 (The term “JP-A” as used herein means an “unexaminedpublished Japanese patent application”) (sulfonylacetic acid salts),JP-A-59-180537 (propionic acid salts), JP-A60-237443(phenylsulfonylacetic acid salts substituted by a sulfonyl group), andJP-A-61-51139 (sulfonylacetic acid salts).

Base precursors consisting of carboxylic acids and organic di ortetra-acidic bases are disclosed in JP-A-63-316760 and JP-A-1-68746(corresponding to U.S. Pat. No. 4,981,965). In these base precursors,the activity on heat treatment at 140° C. is compatible with thestorability. EP0708086 discloses selected base precursors whichsimultaneously satisfy both the activity on heat treatment at 120° C. orless and the storability.

Base precursors each has an inherent decomposition point. However, inpractical applications rapid decomposition of the base precursors (therelease of bases) is expected only at heating temperatures much higherthan their decomposition points. For example, although ease of thedecomposition also is dependent on methods of heating, in order toobtain rapid decomposition at a heating temperature of 120° C., the baseprecursors must usually have a decomposition point of about 100° C. orless.

Other bisguanidine base precursors that are known are described inEP0708086, hereby incorporated by reference. These base precursors canbe employed when it is desirable to rapidly release a base at a lowheating temperatures and have good storability at the same time. Suchbisguanidine salts are selected from the group consisting of a4-(phenylsulfonyl)phenylsulfonylacetic acid salt ofN,N′bis(1,3-diethylguanyl)ethylenediamine, a4(phenylsulfonyl)phenylsulfonylacetic acid salt ofN,N′-bis(1,3diisopropylguanyl)ethylenediamine,4(phenylsulfonyl)phenylsulfonylacetic acid salt ofN,N′-bis-(imidazoline-2yl)ethylenediamine, and other specifiedcompounds.

Base precursors that are neutral or weakly basic compounds that can formrelatively strong bases, in heat developable recording materials, byheat decomposition of the base precursors, are described in U.S. Pat.No. 4,981,965, hereby incorporated by reference. This patent describesbase precursors comprising arylsulfonylacetic acid salts of guanidinebases. Such base precursors have a stable crystal structure, whichcrystal structure is kept until it melts or is dissolved at an elevatedtemperature. Therefore, the carboxylic acid is rapidly decarboxylated torelease a base at the same time that the crystal structure is broken.

When the carboxylic acid has hydrophobic residues, the carboxyl group ofthe carboxylic acid and the organic base are blocked by the hydrophobicresidues in the base precursor of the present invention. Accordingly,the base precursor is prevented by the hydrophobic residue from beingdissolved in a binder (which generally is hydrophilic). The crystalstructure of the salt is further stabilized by intermolecularinteraction between the hydrophobic residues. Therefore, such preferredbase precursors for use in the present compositions exhibit much higherstability during storage when the carboxylic acid has the hydrophobicresidues. Examples of the carboxylic acid are given in the cited U.S.Pat. No. 4,981,965, in columns 9–10.

U.S. Pat. No. 4,981,965 describes the use of guanidinium salts ofarylsulfonylacetic acids as base precursors. The diacidic to tetraacidicbase precursors are composed of two to four guanidinium units. In thesesystems, thermolysis of the salt results in decarboxylation to form aarylsulfonylmethyl anion. This anion abstracts a proton from theguanidinium salt to release the free base. This base can then providethe alkalinity required for a number of image-forming processes.

U.S. Pat. No. 4,060,420 describes the use of ammonium salts ofarylsulfonylacetic acids as activator-stabilizers in photothermographicsystems. In these systems the ammonium species is always a protonatedbasic nitrogen, and thus has at least one labile hydrogen atom. U.S.Pat. No. 4,731,321 discloses ammonium salts of arylsulfonylacetic acidas base precursors in heat-developable lightsensitive materials.

Japanese Patent Application No. 1-150575 discloses thermally releasablebisamines in the form of their bis(arylsulfonylacetic acid) salts. Otheramine-releasing compounds include 2-carboxycarboxamide derivativesdisclosed in U.S. Pat. No. 4,088,496; hydroxylamine carbamates disclosedin U.S. Pat. No. 4,511,650; and aldoxime carbamates disclosed in U.S.Pat. No. 4,499,180.

It is usually desirable for a base precursor to exhibit good stabilityduring storage but to quickly decompose to form a base when it is heatedat the temperature of use. A successful base precursor will not have anyadverse effects on the adjacent layers.

PROBLEM TO BE SOLVED BY THE INVENTION

There is a need for improved base precursor compositions that can beused to permanently and quickly bleach preselected colored components ofin photothermographic systems. Particularly in the field of colorphotothermographic film for consumer use, the requirements in terms ofbleaching and keeping are high.

A problem with prior-art base precursors when used in a filter layer isthat they can cause unacceptable increase of fog densities at theadjacent imaging layers during keeping or during thermal processing.Applicants have found that prior-art base precursors can also causepinholes during thermal processing due to unfavorable diffusion of gasformed during thermal decomposition, rendering the photothermographicelement useless. There is a need for color photothermographic imagingelement comprising an improved base precursor in combination with afilter dye (especially yellow or magenta filter dye) which undergoesefficient and irreversible thermal bleaching during thermal processing.The existence of such imaging chemistry would allow for very rapidlyprocessed films that can be processed simply and efficiently in low costphotoprocessing kiosks.

These and other problems may be overcome by the practice of ourinvention.

SUMMARY OF THE INVENTION

As mentioned above, the present invention is directed to improvedthermal base precursors. Such compounds can be used, for example, tothermally bleaching filter dyes or other components inphotothermographic elements.

This invention also relates to thermal-dye-bleach agents, and inparticular, it relates to salts of arylsulfonylacetic acids as bleachingagents for photothermographic use. Photothermographic elements employingthese thermal-dye-bleach agents are suitable for use as acutance andantihalation systems, bleachable filter dye materials, and in promotingunblocking of various components such as blocked developers.

The use of the thermally bleachable filter dye compositions of thepresent invention can reduce or eliminate pinholes during thermaldevelopment. Such bleachable filter dye compositions also can have theadvantage of reducing or eliminating Dmin increases in the adjacentimaging layers.

Accordingly, the present invention relates to a photothermographicelement comprising a support, at least one aqueous coatablephotothermographic layer, and at least one aqueous coatable colorfilter, wherein the filer layer comprises a heat-bleachable compositioncomprising at least one light-absorbing filter dye that in associationwith a base precursor according to the present invention. Color filtersare commonly used in AHU layers, magenta filter layers, and yellowfilter layers, but the compositions of the present invention can be usedin other layers for filtering purposes, for example, in an imaginglayer.

The term “filter dye” encompasses dyes used in filter layers orantihalation layers and excludes dyes resulting from developing agentsor coupling agents. In one embodiment of the invention, the particlesare dispersed in a matrix comprising a hydrophilic polymer orwater-dispersible hydrophobic polymer.

The invention is also directed to a method of processing aphotothermographic element and the use of the photothermographicelement, wherein the filter layer becomes at least 40%, preferably atleast 50%, more preferably at least 90%, colorless within about 20minutes, preferably within about 5 minutes, more preferably within about0.5 minutes, upon heating to a temperature of at least about 90° C.(according to controlled tests of such a layer essentially alone on thesame support used in the product). The described filter layer isespecially advantageous because of the speed with which the layerbecomes at least 40% colorless upon heating and its good shelf lifestorage stability. Preferred embodiments provide thermal bleaching ofgreater than 50% in less than 20 seconds at a temperature below 175° C.

The invention is also directed to a method of forming an image in themulticolor photothermographic element, including scanning the developedimage.

DETAILED DESCRIPTION OF THE INVENTION

The base precursors of the present invention are useful inphotothermographic materials which usually contain various layers andcomponents, including imaging layers, filter layers, overcoats and thelike. The base precursors comprise novel arylsulfonylacetic acid saltsof guanidine bases.

One aspect of the present invention is directed to an arylsulfonylaceticacid, or photographically acceptable salt thereof, having the followingstructure:

wherein the group Z individually represents the non-metallic atomsnecessary to complete a substituted or unsubstituted ring systemcontaining at least one 5- or 6-membered imide nucleus. For example, animide ring formed by Z may include succinimide, maleimide and congeners,or fused ring systems such as phthalimide and congeners. The atomsrepresented by Z can also complete a 5- or 6-membered imide nucleus thatcan be fused with additional substituted or unsubstituted rings such asa benzo ring. For example, an imide ring formed by Z may also include1,8-naphthalimde.

In the above Structure (I), each of R² and R³ is independently amonovalent group such as hydrogen, an alkyl group, an alkenyl group, acycloalkyl group, an aralkyl group, an aryl group and a heterocyclicgroup. Each of the monovalent groups may have one or more substituentgroups. Among them, hydrogen, an alkyl group and an aryl group arepreferred, and hydrogen is particularly preferred. Each of the alkylgroup, the alkenyl group and the alkynyl group preferably has 1 to 8carbon atoms.

Some examples of specific arylsulfonylacetic acid according to theinvention are as follows:

In a preferred embodiment of the present invention, the base precursorscomprise the salt of an organic base with an arylsufonylacetic acidhaving the following structure:

wherein each of R² and R³ is independently a monovalent group such ashydrogen, an alkyl group, an alkenyl group, a cycloalkyl group, anaralkyl group, an aryl group and a heterocyclic group. Each of themonovalent groups may have one or more substituent groups. Among them,hydrogen, an alkyl group and an aryl group are preferred, and hydrogenis particularly preferred. Each of the alkyl group, the alkenyl groupand the alkynyl group preferably has 1 to 8 carbon atoms.

Each of the R¹ groups may be independently selected from one or moresubstituent groups. Examples of the substituent group include an alkylgroup (preferably having 1 to 10 carbon atoms), an alkoxy group(preferably having 1 to 16 carbon atoms), a halogen atom and analkoxycarbonyl group (preferably having 2 to 16 carbon atoms), all ofwhich may be substituted or unsubstituted. The subscript “n” is 1 to 4,preferably 1 to 2.

These carboxylates undergo decarboxylations on heating therebygenerating the arylsulfonylmethide carbanions. These carbanions in turnabstracts the acidic protons from the guanidinium moieties and stronglybasic guanidines are released. The base precursor composed of acarboxylic acid and an organic base melts or is dissolved in a bindercontained in a recording material at an elevated temperature and thenthe decarboxylation of the carboxylic acid is initiated.

The carboxylic acid of the base precursor of the present inventionshould have such a property that the carboxyl group undergoesdecarboxylation under certain conditions. In the case that the baseprecursor of the present invention is used for a heat developablerecording material, it is preferred that the carboxyl group undergoesdecarboxylation at an elevated temperature. The heating temperaturerequired to decarboxylate the carboxyl group preferably is in the rangeof 80° to 250° C., and more preferably is in the range of 110° to 200°C.

Thus, a base precursor in accordance with the present invention is inthe form of a salt of an organic base with the above-describedcarboxylic acid. In one embodiment of the base precursor of the presentinvention, the organic base is a diacidic to tetraacidic base having thefollowing Structure (II).R¹³(—B)_(n)  (II)

In the Structure (II), R¹³ is an n-valent residue of a hydrocarbon orheterocyclic ring, each of which may have one or more substituentgroups. The “n” is an integer of 2 to 4. The “n” preferably is 2 or 4,and more preferably is 2. When the “n” is 2, it is preferred that thedivalent residue of the hydrocarbon, which may constitute R¹³, is analkylene group (more preferably having 1 to 6 carbon atoms) or anarylene group (more preferably, phenylene). An example of the residue ofthe heterocyclic ring, which may constitute R¹³, is a residue derivedfrom pyridine ring.

The organic base preferably has a symmetrical chemical structure. Thus,it is particularly preferred that the diacidic to tetraacidic basehaving the Structure (III) is symmetrical. In reference to structureStructure (II), the term “symmetrical organic base” means that all ofthe groups represented by “B” are equivalent in the molecular structureof the organic base.

In the Structure (II), the group represented by “B” is preferably amonovalent group corresponding to an atomic group formed by removing onehydrogen atom from a “guanidine moiety” in which the organic base hastwo to four guanidine moieties in its molecular structure. The“guanidine moiety” corresponds to an atomic group formed by removing oneor two hydrogen atoms from a compound (guanidine or a guanidinederivative) having the following Structure (III):

In the Structure (III), each of R¹⁴, R¹⁵, R¹⁶, R¹⁷ and R¹⁸ areindependently a monovalent group such as hydrogen, an alkyl group, analkenyl group, an alkynyl group, a cycloalkyl group, an aralkyl group,an aryl group and a heterocyclic group. Each of the monovalent groupsmay have one or more substituent groups. Each of the alkyl group,alkenyl group, alkynyl group, cycloalkyl group, aralkyl group, arylgroup and heterocyclic group preferably has 1 to 6 carbon atoms(including carbon atoms contained in substituent groups). Hydrogen, analkyl group, a cycloalkyl group, an aralkyl group and an aryl group arepreferred. Hydrogen and an alkyl group are more preferred. Hydrogen ismost preferred. An example of the cycloalkyl group is cyclohexyl. Anexample of the aralkyl group is benzyl. An example of the aryl group isphenyl.

Any two of R¹⁴, R¹⁵, R¹⁶, R¹⁷ and R¹⁸ may be combined together to form afive-membered or six-membered nitrogen containing heterocyclic ring. Theheterocyclic ring preferably consists of nitrogen and carbon atoms. Inother words, the five or six members of the ring preferably are onlynitrogen and carbon atoms.

It is particularly preferred that the organic base or compound havingthe Structure (II) above is guanidine (having no substituent group),more preferably, a diacidic to tetraacidic base that is composed of twoto four guanidine moieties corresponding to an atomic group formed byremoving one or two hydrogen atoms from the above-mentioned compoundhaving the Structure (III) and at least one linking group for theguanidine moieties.

The linking group is a residue of a hydrocarbon or a heterocyclic ring.The hydrocarbon may be a linear aliphatic, alicyclic or aromaticcompound. Examples of the heterocyclic ring include pyridine andtriazine. The linking group may have one or more substituent groups.

Examples of the substituent group include an alkyl group (preferablyhaving 1 to 6 carbon atoms), an alkoxy group (preferably having 1 to 6carbon atoms), a halogen atom and hydroxyl. The linking group preferablyhas 1 to 10 carbon atoms (including carbon atoms contained insubstituent groups), more preferably has 1 to 8 carbon atoms, and mostpreferably has 1 to 6 carbon atoms.

The guanidine moiety preferably is a monovalent substituent group of ahydrocarbon or heterocyclic ring, as shown in the Structure (III) above.In other words, it is preferred that the guanidine moiety corresponds toan atomic group formed by removing one hydrogen atom from an guanidinehaving the Structure (III), but the guanidine moiety may correspond toan atomic group formed by removing two hydrogen atoms from suchguanidine. In this case, the organic base may be in the form of anitro-containing heterocyclic ring (e.g., a pyperazine ring).

Examples of the organic base which can be used in the base precursor ofthe present invention are given in U.S. Pat. No. 4,981,965, herebyincorporated by reference in its entirety.

In one preferred embodiment of the present invention, the salt of anorganic baseis a bisguanidinium salt having the following formula:

wherein n is 2, 3 or 4.

Examples of some preferred salts of organic bases are the following:

In one preferred embodiment of the invention, base precursors accordingto the present invention can be represented by the following Structure(IV):

wherein n is 2, 3, or 4 and Z, R² and R³ are as defined above withrespect to Structure (I).

Some examples of some specific preferred base precursors are as follows:

In one embodiment of the invention, base precursors in accordance withthe present invention are useful for promoting reactions that require analkaline environment, for example the unblocking of a blockedphotographically useful compound. Such compounds include, but are notlimited to, couplers, development inhibitors, bleach accelerators,bleach inhibitors, inhibitor releasing developers, dye precursors,developing agents, electron transfer agents, silver halide solvents,silver halide complexing agents, reductones, image toners,pre-processing or post-processing image stabilizers, hardeners, orprecursors thereof.

In one embodiment of the invention, base precursors in accordance withthe present invention are useful in a filter layer of aphotothermographic element to absorb light of a color not completelyabsorbed by a color layer or color layer unit above the filter layer,while transmitting light of a color intended to be absorbed by a colorlayer or a color layer below the filter layer. A filter layer willtypically employ a filter dye, which absorbs, or filters out, light notintended to be absorbed by a color layer. An antihalation dye can beviewed as a type of filter layer positioned below all the color layers,although no light needs to be transmitted to any color layer below theantihalation layer. In any case, however, it is necessary that passageof light through the antihalation unit (namely, back through theantihalation unit by reflection) is prevented or minimized. Thus, it maybe said that filter-dye compositions absorb light from different regionsof the spectrum, such as red, blue, green, ultraviolet, and infrared, toname a few, and that such filter-dye compositions perform the functionof absorbing light during exposure of the material so as to prevent orat least inhibit light of a specific spectral region from reaching atleast one of the radiation sensitive layers of the element. Dyes arealso used in color photographic materials as filters, typically locatedin overcoats or interlayers, to absorb incident radiation and improveimage sharpness.

It is generally desirable for both photothermographic and conventionalwet-processed films to employ light-filtering filter-dye compositionsthat can be quickly and readily rendered ineffective, i.e., decolorizedor destroyed and removed, either prior to, during, or after photographicprocessing.

Imaging elements that can be processed, after imagewise exposure, byheating the element are referred to as photothermographic elements.Although not essential, it would be desirable for a filter layer in aphotothermographic element to be capable of being rendered substantiallydecolorized upon heat processing in order to avoid unwanted absorptionof light during subsequent scanning. Such unwanted absorption mightotherwise cause an undesirably higher level of minimum density (anincreased “D_(min)”). Particularly in the case of a colorphotothermographic film, bleaching a filter layer to colorless or lesscolored and avoiding or minimizing any tint, subsequent to image capturebut prior to scanning, is desirable.

The de-coloration or destruction of a light-absorbing dye willhereinafter be referred to as bleaching. In the case ofphotothermographic films, which are processed in the absence ofprocessing baths, in the simplest case the bleaching must occur byheating.

Prior-art dyes having desirable absorption characteristics for use as afilter dye have not always had good thermal-bleaching characteristics.Visible images made from photographic elements containing such dyes havebeen subject to undesirable stains. Other prior-art thermally bleachabledye compositions have not had the desired stability that is required fornormal storage of the photographic element, particularly when such dyesare used in combination with a base precursor subject to premature baserelease. Many otherwise dry photographic processes (i.e., thosephotographic processes that require no liquids for the preparation of avisible image) have employed light-absorbing dyes that could only beremoved by subjecting them to some form of liquid treatment for example,an acid bath or an alkaline bath. However, many of these otherwise dryprocesses lose their attractiveness when liquids are required for dyeremoval. Typical processes employing prior-art light-absorbing layersare described in U.S. Pat. No. 3,260,601 and U.S. Pat. No. 3,282,699,herein incorporated by reference.

A further problem is that dark keeping of a thermally bleachable dyecomposition is especially challenging in the case of aphotothermographic color film for consumer use. For such compositions tobe useful, it would be crucial that they have the least amount ofdark-keeping loss, and at the same time undergo almost completebleaching at higher temperatures.

A variety of filter compositions have been reported in the literaturefor use in photothermographic systems, which compositions avoid the useof processing solutions. For example, prior patents or publications ofrelevance include U.S. Pat. No. 5,312,721, EP 708,086 A1, EP 911,693 A1,U.S. Pat. No. 4,981,965, U.S. Pat. No. 5,258,274, U.S. Pat. No.4,197,131, Research Disclosure, 1978, 170, 40–41, Research Disclosure,1978, 169, 44–45, Research Disclosure, 16978 (1978), ResearchDisclosure, 19721 (1980), hereby all incorporated by reference in theirentirety.

The use of base precursors for use in combination with filter dyes (asantihalation layers) in photothermographic and thermographic systems aregenerally known. They can be used in heat processable photosensitiveelements that can be constructed so that after exposure, they can beprocessed in a substantially dry state, or with small amounts of water,by applying heat. Because of the much greater challenges involved indeveloping a dry or substantially dry color photothermographic system,however, most of the activity and success to date has been limited toblack-and-white photothermographic systems, especially in the areas ofhealth imaging and microfiche.

In general, when reference in this application is made to a particularmoiety or group it is to be understood that such reference encompassesthat moiety whether unsubstituted or substituted with one or moresubstituents (up to the maximum possible number). For example, “alkyl”or “alkyl group” refers to a substituted or unsubstituted alkyl, while“benzene group” refers to a substituted or unsubstituted benzene (withup to six substituents). Generally, unless otherwise specificallystated, substituent groups usable on molecules herein include anygroups, whether substituted or unsubstituted, which do not destroyproperties necessary for the photographic utility. Examples ofsubstituents on any of the mentioned groups can include knownsubstituents, such as: halogen, for example, chloro, fluoro, bromo,iodo; hydroxy; alkoxy, particularly those “lower alkyl” (that is, with 1to 6 carbon atoms, for example, methoxy, ethoxy; substituted orunsubstituted alkyl, particularly lower alkyl (for example, methyl,trifluoromethyl); thioalkyl (for example, methylthio or ethylthio),particularly either of those with 1 to 6 carbon atoms; substituted orunsubstituted alkenyl, preferably of 2 to 10 carbon atoms (for example,ethenyl, propenyl, or butenyl); substituted and unsubstituted aryl,particularly those having from 6 to 20 carbon atoms (for example,phenyl); and substituted or unsubstituted heteroaryl, particularly thosehaving a 5 or 6-membered ring containing 1 to 3 heteroatoms selectedfrom N, O, or S (for example, pyridyl, thienyl, furyl, pyrrolyl); acidor acid salt groups such as any of those described below; hydroxylate,amino, alkylamino, cyano, nitro, carboxy, carboxylate, acyl,alkoxycarbonyl, aminocarbonyl, sulfonamido, sulfamoyl, sulfo, sulfonate,alkylammonium, and an ionizable group with a pKa value below 4 in water;and others known in the art. Alkyl substituents may specifically include“lower alkyl” (that is, having 1–6 carbon atoms), for example, methyl,ethyl, and the like. Further, with regard to any alkyl group or alkylenegroup, it will be understood that these can be branched or unbranchedand include ring structures.

The combination of a dye with an improved base precursor of the presentinvention, as mentioned above, finds particular utility as antihalationor acutance constructions in photothermographic materials, e.g., drysilver materials, since the dyes will readily bleach during the thermalprocessing of the materials. In principle, the dye may be any dyecapable of being bleached by the base precursors of the invention.

Other bleachable dyes include benzothiazines [cite other docket];cyanines as disclosed in US EP0911693, hereby incorporated by reference,polymethine dyes, and other dyes capable of being bleached by thethermal-carbanion-generating agents of the invention. One preferredclass of dyes are polymethine dyes. These are disclosed, for example, inW. S. Tuemmler and B. S. Wildi, J. Amer. Chem. Soc. 1958, 80, 3772; H.Lorenz and R. Wizinger, Helv. Chem. Acta. 1945, 28, 600; U.S. Pat. Nos.2,813,802, 2,992,938, 3,099,630, 3,275,442, 3,436,353 and 4,547,444; andJapanese Patent No. 56109,358. The dyes have found utility in infraredscreening compositions, as photochromic materials, as sensitizers forphotoconductors, and as infrared absorbers for optical data storagemedia. Polymethine dyes have been shown to bleach in conventionalphotographic processing solutions, as disclosed in European PatentPublication No. EP 0,377,961, but have not previously been known tobleach by thermal-carbanion-generating processes.

One preferred class of dyes are barbituric acid arylidene dyes thatundergo efficient thermal bleaching in the presence of base precursorsin gelatin coatings. In one preferred embodiment, arylidene dyes can berepresented by the following Structure (I):

wherein A is derived from an acidic moiety, and D and R are as definedbelow. The acidic moiety comprises a cyclic ketomethylene moiety.Examples of a cyclic ketomethylene moiety is barbituric acid andsubstituted or unsubstituted derivatives thereof. In a particularlypreferred embodiment, the A group is represented by the followingstructure (II):

wherein R¹ and R² each individually represent a hydrogen, an alkyl group(“group” wherever used in the present application including thepossibility of being substituted or unsubstituted alkyl) of 1 to 20(preferably 1 to 8) carbon atoms; or an aryl, aralkyl, heterocyclic orcycloalkyl group of 5 to 14 carbon atoms.

The group R in the above structure I represents hydrogen, an aryl groupcontaining 6 to 14 carbon atoms, or an alkyl group containing 1 to 12carbon atoms (which groups may be substituted). The group D in the abovestructure I may be an aryl or heteroaryl ring. The group D maypreferably contains an atom with an available electron pair positionedin conjugation (with the carbonyl oxygens of the barbituric acid ringwhen A represents a barbituric acid nucleus in Formula I), said atombeing an O, N, Se, S in a ring system or as a substituent on such aring. D may particularly contain an O or N atom positioned in a ring inconjugation. By being positioned in “conjugation” with the carbonyloxygen, it is meant that there is a conjugated system between the oxygenand the atom in D. Such systems are generally known in organic chemistryand refer to a chain in which a single bond, and a double or triplebond, appear alternately.

Some examples of preferred groups for D include:

The groups R⁶, R¹¹ and R¹² each individually represents hydrogen,carboxy, carboxyalkyl, sulfonamido, sulfamoyl, or an alkyl, arylalkyl,cycloalkyl, alkoxy, alkylamino, or alkylthio group preferably of 1 to 10carbon atoms. The groups R⁴ and R⁵ each individually represents an alkylgroup, such as CHR¹¹R¹², preferably of 1 to 20 (and more preferably 1 to8) carbon atoms or an alkenyl group preferably of 2 to 8 carbon atoms,or an aryl, arylalkyl, heterocyclic or cycloalkyl group preferably of 5to about 14 carbon atoms. Alternatively, R⁴ and R⁵ together representthe non-metallic atoms required to form a substituted or unsubstituted5- or 6-membered ring with each other, or R⁴ and R⁵ individuallyrepresent the non-metallic atoms necessary to form a substituted orunsubstituted 5- or 6-membered fused ring with the phenyl ring to whichthe nitrogen is attached. Preferred substituents, particularly on alkylgroups include carboxy, carboxyalkyl and sulfonamido.

The subscript “n” is 0, 1, 2, 3 or 4, preferably zero; the subscript “p”is 0, 1, 2, 3, 4 or 5, preferably 1 to 3.

The group Z individually represents the non-metallic atoms necessary tocomplete a substituted or unsubstituted ring system containing at leastone 5- or 6-membered heterocyclic nucleus. For example, a ring systemformed by Z may include pyridine, pyrazole, pyrrole, furan, thiophene,and congeners, or fused ring systems such as indole, benzoxazole, andcongeners. The atoms represented by Z can also complete a 5- or6-membered heterocyclic nucleus that can be fused with additionalsubstituted or unsubstituted rings such as a benzo ring. Suitableheterocyclic nuclei are of the type commonly used in sensitizing dyesand are well known in the art. Many are described, for example, inJames, The Theory of the Photographic Process, 4th Edition, pages195–203. Useful heterocyclic nuclei include thiazole, selenazole,oxazole, imidazole, indole, benzothiazole, benzindole, naphthothiazole,naphthoxazole, benzimidazole, and the like. In a preferred embodiment, Zrepresents the atoms necessary to complete a substituted orunsubstituted benzoxazole or benzothiazole nucleus.

Examples of any of the alkyl groups mentioned above are methyl, ethyl,propyl, isopropyl, butyl, isobutyl, t-butyl, pentyl, hexyl, octyl,2-ethylhexyl, and congeners. Cycloalkyl groups can be cyclopentyl,cyclohexyl, 4-methylcyclohexyl, and congeners. Alkenyl groups can bevinyl, 1-propenyl, 1-butenyl, 2-butenyl, and congeners. Aryl groups canbe phenyl, naphthyl, styryl, and congeners. Arylalkyl groups can bebenzyl, phenethyl, and congeners. Useful substituents on any of theforegoing or other groups disclosed, include halogen, alkoxy, acyl,alkoxycarbonyl, aminocarbonyl, carbonamido, carboxy, sulfamoyl,sulfonamido, sulfo, nitro, hydroxy, amino and congeners.

In a preferred embodiment, the compounds of Structure I above arebarbituric acid arylidene dyes represented by the

In a preferred embodiment, D is selected from the following groups:

Structures of some exemplary barbituric acid arylidene dyes are asfollows:

D-1

D-2

D-3

D-4

D-5

D-6

D-7

D-8

In a preferred embodiment, as indicated above, the above dyes are usedas a yellow or magenta filter dye in a photothermographic element. Thedyes such as D-1, D-2, D-3, D-4, D-5, D-6 and D-7 are suitable as yellowfilter dyes. The dye D-8 may be suitable as a magenta filter dye. Thebarbituric acid arylidene dyes undergo efficient thermal bleaching inthe presence of base precursors of the present invention.

As indicated above, in principle, any dye capable of being bleached bythe base precursors of the invention can be employed.

If desired, a combination of dye compounds can be used. Selection of thedye combinations will depend upon such factors as the processingconditions, desired degree of bleaching in the layer containing the dyeor dyes, solubility characteristics of the components, spectralabsorption characteristics, and the like.

The filter dye should be changed to the extent that at least about 40%,and preferably at least 50%, more preferably at least 60%, still morepreferably at least 80%, and most preferably at least 90% of the layerabsorption is changed from colored to colorless according to a standardtest using Status M density. Thus, the filter layer, after bleaching,has minimal or substantially no optical density that will adverselyaffect the Dmin of the product during scanning, or during overallpicture production using the photothermographic element.

More than one type of filter dye can be used in the same filter layer.Combinations of different filter dyes can be used in the same layer orin different layers, depending on the purpose of the dye. Preferably,the filter dyes useful in an filter layer according to the presentinvention, if yellow, absorbs mainly from about 400 to about 500 nm andwill transmit most of the light in the range 500 to 850 nm. Preferably,a yellow filter dye will absorb mainly at from about 420 to about 480 nmand will transmit most of the light in the range 490 to 850 nm.Similarly, a magenta filter dye will absorb light mostly from 500 to 600nm and preferably from 520 to 580 nm while transmitting most of thelight shorter than 500 nm and longer than 600 nm.

Optional means, which may be additional to bleachable filter dyes, forabsorbing yellow include Carey Lea silver or a yellow processingsolution decolorizable dye. Other suitable yellow filter dyes can beselected from among those illustrated by Research Disclosure I, SectionVIII. Absorbing and scattering materials, B. Absorbing materials.

The filter dyes within the photothermographic elements can beirreversibly bleached upon exposure to heat of adequate intensity,including dry processing, in the presence of the improved baseprecursors of the present invention.

For black & white or monochromatic imaging elements, the phototographicelements are typically based on organic silver salt oxidizing agents andorganic reducing agents are described in Owen U.S. Pat. No. 2,910,377,wherein are included silver behenate and silver stearate as well as thesilver salts of a number of other organic acids, viz oleic, lauric,hydroxystearic, acetic, phthalic, terephthalic, butyric, m-nitrobenzoic,salicylic, phenylacetic, pyromellitic, p-phenylbenzoic, undecylenic,camphoric, furoic, acetamidobenzoic, and o-aminobenzoic. Other organicsilver salts capable of providing similar effects include the silversalts of saccharin, benzotriazole, phthalazinone,4′-n-octadecyloxydiphenyl-4-carboxylic acid, 10,12,14-octadecatrienoicacid, and benzoic acid. The silver salts of those organic acids whichare water-insoluble and normally solid are preferred, since thebyproducts do not adversely affect the coating.

Filter dye compositions in accordance with ththe present invention havegood incubation stability, allowing their incorporation into elementsrequiring prolonged storage. The dyes contained in the novelphotothermographic elements of this invention are irreversibly bleachedupon exposure to heat. The amount of heat required to cause bleaching ofthe layers is somewhat dependent upon the particular dye incorporated inthe layer; higher temperatures require shorter times to bring aboutbleaching while lower temperatures require longer times. Generally,temperatures of at least 125° C. for a period of at least 5 seconds arerequired to bring about any noticeable bleaching. For colorphotothermography, temperatures of 130° C. and above and times in excessof 10 seconds are generally preferred.

The dyes incorporated in the novel layers of this invention arecharacterized by their good spectral absorption properties. The maximumabsorption of the various individual dyes ranges throughout the visibleregions of the spectrum.

The dyes described herein can be used to make light-absorbing layersincluding filter layers with or without dyes of other classes and can beincorporated readily in colloidal binders used for forming such layers.They are especially useful in gelatin layers lying adjacent to silverhalide layers.

The photographic elements prepared according to the instant inventioncan be used in various kinds of photothermographic systems. In additionto being useful in X-ray and other non-optically sensitized systems,they can also be used in orthochromatic, panchromatic and infraredsensitive systems. The sensitizing addenda can be added to photographicsystems before or after any sensitizing dyes which are used.

The dyes used in this invention can be used in emulsions intended forcolor photothermography, for example, emulsions containing color-formingcouplers or other color-generating materials, emulsions of themixed-packet type such as described in U.S. Pat. No. 2,698,794 ofGodowsky issued Jan. 4, 1955; in silver dye-bleach systems; andemulsions of the mixed-grain type such as described in U.S. Pat. No.2,592,243 of Carroll and Hanson issued Apr. 8, 1952.

Photographic layers containing filter dyes can also be used in colortransfer processes which utilize the diffusion transfer of an imagewisedistribution of developer, coupler or dye from a light-sensitive layerto a second layer while the two layers are in close proximity to oneanother. Color transfer processes of this type are described in Yutzy,U.S. Pat. No. 2,856,142; Land et al. U.S. Pat. No. 2,983,606; Whitmoreet al. British Pat. Nos. 904,364 and 840,731; and Whitmore et al. U.S.Pat. No. 3,227,552.

Depending on the choice of the filter dye, it can be in the filter layerin the form of solid particles, dissolved in a dispersed organic phase,emulsified, or dissolved in the aqueous matrix of the filter layer.Although dissolving a water-soluble dye in the aqueous matrix iseasiest, it is not universally preferred since one would generallyprefer that the dye remain in the layer in which it was coated.

The coverages and proportions of the components which comprise thedescribed filter component of the present invention can vary over wideranges depending upon such factors as the particular use, location inthe element of the filter component, the desired degree of absorption,processing temperatures, and the like. For example, in somephotothermographic elements the concentration of dye is sufficient toprovide a peak optical density of at least about 0.05. Particles of thefilter dyes can be made by conventional dispersion techniques, such asmilling, by preparing the particles by a limited coalescence procedure,or other procedures known in the art. Milling processes that can be usedinclude, for example, processes described in U.K. Patent No. 1,570,632,and U.S. Pat. Nos. 3,676,147, 4,006,025, 4,474,872 and 4,948,718, theentire disclosures of which are incorporate herein by reference. Limitedcoalescence procedures that can be used include, for example, theprocedures described in U.S. Pat. Nos. 4,994,3132, 5,055,371, 2,932,629,2,394,530, 4,833,060, 4,834,084, 4,965,131 and 5,354,799, the entiredisclosures of which are incorporated herein by reference. A suitableaverage size of the particles are 10 to 5000 nm, preferably 20 to 1000nm, most preferably 30 to 500 nm.

In a preferred embodiment, the filter dye is dispersed in the binder inthe form of a solid particle dispersion. Such dispersions can be formedby either milling the dye in solid form until the desired particle sizerange is reached, or by precipitating (from a solvent solution) the dyedirectly in the form of a solid particle dispersion. In the case ofsolid particle milling dispersal methods, a coarse aqueous premix,containing the barbituric acid arylidene compound and water, andoptionally, any desired combination of water soluble surfactants andpolymers, is made, and added to this premix prior to the millingoperation. The resulting mixture is then loaded into a mill. The millcan be, for example, a ball mill, media mill, jet mill, attritor mill,vibratory mill, or the like. The mill is charged with the appropriatemilling media such as, for example, beads of silica, silicon nitride,sand, zirconium oxide, yttria-stabilized zirconium oxide, alumina,titanium, glass, polystyrene, etc. The bead sizes typically range from0.25 to 3.0 mm in diameter, but smaller media may be used if desired.The solid barbituric acid arylidene in the slurry are subjected torepeated collisions with the milling media, resulting in crystalfracture and consequent particle size reduction.

The aqueous dispersion can further contain appropriate surfactants andpolymers previously disclosed for use in making pH precipitateddispersions. For solvent precipitation, a solution of the dye is made insome water miscible, organic solvent. The solution of the dye is addedto an aqueous solution containing appropriate surfactants and polymersto cause precipitation as previously disclosed for use in making solventprecipitated dispersions.

Surfactants and other additional conventional addenda may also be usedin the dispersing process described herein in accordance with prior artsolid particle dispersing procedures. Such surfactants, polymers andother addenda are disclosed in U.S. Pat. Nos. 5,468,598, 5,300,394,5,278,037, 4,006,025, 4,924,916, 4,294,917, 4,940,654, 4,950,586,4,927,744, 5,279,931, 5,158,863, 5,135,844, 5,091,296, 5,089,380,5,103,640, 4,990,431,4,970,139, 5,256,527, 5,015,564, 5,008,179,4,957,857, and 2,870,012, British Patent specifications Nos. 1,570,362and 1,131,179 referenced above, the disclosures of which are herebyincorporated by reference, in the dispersing process of the filter dyes.

Additional surfactants or other water soluble polymers may be addedafter formation of the dye dispersion, before or after subsequentaddition of the small particle dispersion to an aqueous coating mediumfor coating onto a photographic element support. The aqueous mediumpreferably contains other compounds such as stabilizers and dispersants,for example, additional anionic nonionic, zwitterionic, or cationicsurfactants, and water soluble binders such as gelatin as is well knownin the photographic element art. The aqueous coating medium may furthercontain other dispersion or emulsions of compounds useful inphotography. Another technique for forming solid dye particles involvessolvent precipitation. For example, a solution of the dye can be made insome water miscible, organic solvent, after which the solution of thedye can be added to an aqueous solution containing appropriatesurfactants and polymers to cause precipitation.

Various techniques for forming a liquid dispersion of the filter dye,including oil-in-water emulsions, are well known by the skilled artisan.An oil-in-water dispersion of the dye may be prepared by dissolving thedye in an organic liquid, forming a premix with an aqueous phasecontaining dispersing aids such as water-soluble surfactants, polymersand film forming binders such as gelatin, and passing the premix througha mill until the desired particle size is obtained. The mill can be anyhigh energy device such as a colloid mill, high pressure homogenizer,ultrasonic device, or the like. Preparation of conventional oil-in-waterdispersions are well known in the art and are described in furtherdetail, for example, in Jelly and Vittum U.S. Pat. No. 2,322,027.Alternatively, the filter dye can be loaded into a latex polymer, eitherduring or after polymerization, and the latex can be dispersed in abinder. Additional disclosure of loaded latexes can be found in MillikenU.S. Pat. No. 3,418,127.

In a preferred embodiment, the base precursor is also dispersed in thebinder as a solid particle dispersion. All prior descriptions ofdispersion milling techniques, formulations and procedures that havedescribed the incorporation of the filter dye are also applicable toincorporation of the base precursor.

For aqueous imaging systems, the binders used in the aqueous dispersionor coating composition should be transparent or translucent and includethose materials which do not adversely affect the reaction which changesthe dye from colored to colorless and which can withstand the processingtemperatures employed. These polymers include, for example, proteinssuch as gelatin, gelatin derivatives, cellulose derivatives,polysaccharides such as dextran and the like; and synthetic polymericsubstances such as water soluble polyvinyl compounds like poly(vinylalcohol), poly(vinyl pyrrolidone), acrylamide polymers and the like.Other synthetic polymeric compounds which can be useful includedispersed vinyl compounds such as styrene butadiene rubbers in latexform. Effective polymers include high molecular weight materials,polymers and resins which are compatible with the imaging materials ofthe element. Combinations of the described colloids and polymers canalso be useful if desired.

A preferred embodiment of the invention is a photothermographic elementcomprising (a) a support having thereon (b) a photothermographic layer,and on the support or in the support (c) at least one filter dyecompound represented by the Structure (I), as described above, whereinthe dye becomes at least about 50, preferably at least 70% colorlesswithin about 30 seconds upon heating to a temperature of at least about150° C., as determined by standard testing described herein. Preferablythe support is suitably transparent for scanning purposes.

A visible image can be developed in a photothermographic elementaccording to the invention within a short time after imagewise exposuremerely by uniformly heating the photothermographic element to moderatelyelevated temperatures. For example, the photothermographic element canbe heated, after imagewise exposure, to a temperature within the rangewhich provides development of the latent image and also provides thenecessary temperature to cause the filter layer to change from coloredto colorless. Heating is typically carried out until a desired image isdeveloped and until the filter layer is bleached to a desired degree.This heating time is typically a time within about 1 second to about 20minutes, such as about 1 second to about 90 seconds.

As indicated above, the filter layer as described can be useful in avariety of photothermographic elements. For example, suchphotothermographic elements are used in the field of microfilming,health imaging, graphic arts, consumer products, and the like. In thefield of health or medical imaging, the originating exposure may beX-ray, for example, followed by the use of phosphorescent light forexposing the film. A preferred use of the present invention, however, isin consumer color photothermographic film that is to be scanned,especially scanning turbid film as when the film is scanned withoutfirst removing the silver in the film, in which situation the bleachingof the dye will contribute to a low Dmin.

The described combination of a filter dye and base precursor can be inany suitable location in the photothermographic element which providesthe desired bleaching of the dye upon heating. Typically, the inventivelayer must be coated on the same side of the support as the radiationsensitive layers. In one embodiment of the invention, the dye is inassociation with a base precursor or base precursor to promote thedesired heat bleaching in the filter component. The term “inassociation” as employed herein is intended to mean that the describedmaterials are in a location with respect to each other which enables thedesired processing and heat bleaching and provides a more usefuldeveloped image. The term is also employed herein to mean that thefilter dye and the base precursor are in a location with respect to eachother which enables the desired change of the dye from colored tocolorless upon heating as described. In general, the two componentsshould be in the same layer, meaning there is no significant barrier ordistance between them even if not uniformly dispersed together.Preferably, however, the filter dye and the base precursor are uniformlyinter-dispersed. Alternatively, however, a sufficient amount of baseprecursor may transfer from an adjacent imaging layer before and duringthermal processing.

A simple exemplary photothermographic element, showing one embodimentcomprising filter layers and their placement in the element, can berepresented as follows:

UV Overcoat Blue Sensitive Layer Yellow Filter Layer Green SensitiveLayer Magenta Filter Layer Red Sensitive Layer AHU Layer Support

As indicated above, the invention is especially useful in a dryphotothermographic process (or “dry thermal process”). By a “dry thermalprocess” is meant herein a process involving, after imagewise exposureof the photographic element, development of the resulting latent imageby the use of heat to raise the temperature of the photothermographicelement or film to a temperature of at least about 80° C., preferably atleast about 100° C., more preferably at about 120° C. to 180° C., in adry process or an apparently dry process. By a “dry process” is meantwithout the external application of any aqueous solutions. By an“apparently dry process” is meant a process that, while involving theexternal application of at least some aqueous solutions, does notinvolve an amount more than the uniform saturation of the film withaqueous solution.

This dry thermal process typically involves heating thephotothermographic element until a developed image is formed, such aswithin about 0.5 to about 60 seconds. By increasing or decreasing thethermal processing temperature a shorter or longer time of processing isuseful. Heating means known in the photothermographic arts are usefulfor providing the desired processing temperature for the exposedphotothermographic element. The heating means can, for example, be asimple hot plate, iron, roller, heated drum, microwave heater, heatedair, vapor or the like. Thermal processing is preferably carried outunder ambient conditions of pressure and humidity, for simplicity sake,although conditions outside of normal atmospheric pressure and humidityare also useful.

A dry thermal process for the development of a color photothermographicfilm for general use with respect to consumer cameras providessignificant advantages in processing ease and convenience, since theyare developed by the application of heat without wet processingsolutions. Such film is especially amenable to development at kiosks orat home, with the use of essentially dry equipment. Thus, the dryphotothermographic system opens up new opportunities for greaterconvenience, accessibility, and speed of development (from the point ofimage capture by the consumer to the point of prints in the consumer'shands), even essentially “immediate” development in the home for a widecross-section of consumers.

Preferably, during thermal development an internally located blockeddeveloping agent, in reactive association with each of threelight-sensitive units, becomes unblocked to form a developing agent,whereby the unblocked developing agent is imagewise oxidized ondevelopment. It is necessary that the components of the photographiccombination be “in association” with each other in order to produce thedesired image. The term “in association” herein means that, in thephotothermographic element, the photographic silver halide and theimage-forming combination are in a location with respect to each otherthat enables the desired processing and forms a useful image. This mayinclude the location of components in different layers.

A typical color photothermographic element will now be described. Thesupport for the photothermographic element can be either reflective ortransparent, which is usually preferred. When reflective, the support iswhite and can take the form of any conventional support currentlyemployed in color print elements. When the support is transparent, itcan be colorless or tinted and can take the form of any conventionalsupport currently employed in color negative elements-e.g., a colorlessor tinted transparent film support. Details of support construction arewell understood in the art. Examples of useful supports arepoly(vinylacetal) film, polystyrene film, poly(ethyleneterephthalate)film, poly(ethylene naphthalate) film, polycarbonate film, and relatedfilms and resinous materials, as well as paper, cloth, glass, metal, andother supports that withstand the anticipated processing conditions. Theelement can contain additional layers, such subbing layers and the like.Transparent and reflective support constructions, including subbinglayers to enhance adhesion, are disclosed in Section XV of ResearchDisclosure I.

The filter dyes of the present invention can be used in the AHU layer,the yellow filter layer, or the magenta filter layer in the abovephotothermographic element. In such an embodiment, the photosensitivelayers are coated from aqueous melts on a transparent support with a(thermally bleachable) AHU (antihalation undercoat), an overcoatcontaining UV protection, a (thermally-bleachable) yellow filter layerbetween the blue-sensitized and green-sensitized records, and themagenta filter dye layer between the green-sensitized and red-sensitizedlayers. The magenta filter layer is typically under the green record andprovides substantially no red absorption. This magenta filter layer is anon-light-sensitive interlayer located further from the support than anyred-sensitized layer, and closer to the support than anygreen-sensitized layer. Similarly, a yellow filter layer is typicallyunder the blue record and provides substantially no green absorption.This yellow filter layer is a non-light-sensitive interlayer locatedfurther from the support than any green-sensitized layer, and closer tothe support than any blue-sensitized layer.

Photographic elements may also usefully include a magnetic recordingmaterial as described in Research Disclosure, Item 34390, November 1992,or a transparent magnetic recording layer such as a layer containingmagnetic particles on the underside of a transparent support as in U.S.Pat. No. 4,279,945, and U.S. Pat. No. 4,302,523.

In an example (one embodiment) of a color negative film construction,each of blue, green and red recording layer units BU, GU and RU areformed of one or more hydrophilic colloid layers and contain at leastone radiation-sensitive silver halide emulsion and coupler, including atleast one dye image-forming coupler. It is preferred that the green, andred recording units are subdivided into at least two recording layersub-units to provide increased recording latitude and reduced imagegranularity. In the simplest contemplated construction each of the layerunits or layer sub-units consists of a single hydrophilic colloid layercontaining emulsion and coupler. When coupler present in a layer unit orlayer sub-unit is coated in a hydrophilic colloid layer other than anemulsion containing layer, the coupler containing hydrophilic colloidlayer is positioned to receive oxidized color developing agent from theemulsion during development. Usually the coupler containing layer is thenext adjacent hydrophilic colloid layer to the emulsion containinglayer.

BU contains at least one yellow dye image-forming coupler, GU containsat least one magenta dye image-forming coupler, and RU contains at leastone cyan dye image-forming coupler. Any convenient combination ofconventional dye image-forming couplers can be employed. Conventionaldye image-forming couplers are illustrated by Research Disclosure I,cited above, X. Dye image formers and modifiers, B. Image-dye-formingcouplers. The photographic elements may further contain otherimage-modifying compounds such as “Development Inhibitor-Releasing”compounds (DIR's). Useful additional DIR's for elements of the presentinvention, are known in the art and examples are described in U.S. Pat.Nos. 3,137,578; 3,148,022; 3,148,062; 3,227,554; 3,384,657; 3,379,529;3,615,506; 3,617,291; 3,620,746; 3,701,783; 3,733,201; 4,049,455;4,095,984; 4,126,459; 4,149,886; 4,150,228; 4,211,562; 4,248,962;4,259,437; 4,362,878; 4,409,323; 4,477,563; 4,782,012; 4,962,018;4,500,634; 4,579,816; 4,607,004; 4,618,571; 4,678,739; 4,746,660;4,746,601; 4,791,049; 4,857,447; 4,865,959; 4,880,342; 4,886,736;4,937,179; 4,946,767; 4,948,716; 4,952,485; 4,956,269; 4,959,299;4,966,835; 4,985,336 as well as in patent publications GB 1,560,240; GB2,007,662; GB 2,032,914; GB 2,099,167; DE 2,842,063, DE 2,937,127; DE3,636,824; DE 3,644,416 as well as the following European PatentPublications: 272,573; 335,319; 336,411; 346,899; 362,870; 365,252;365,346; 373,382; 376,212; 377,463; 378,236; 384,670; 396,486; 401,612;401,613.

DIR compounds are also disclosed in “Developer-Inhibitor-Releasing (DIR)Couplers for Color Photography,” C. R. Barr, J. R. Thirtle and P. W.Vittum in Photographic Science and Engineering, Vol. 13, p. 174 (1969),incorporated herein by reference.

It is common practice to coat one, two or three separate emulsion layerswithin a single dye image-forming layer unit. When two or more emulsionlayers are coated in a single layer unit, they are typically chosen todiffer in sensitivity. When a more sensitive emulsion is coated over aless sensitive emulsion, a higher speed is realized than when the twoemulsions are blended. When a less sensitive emulsion is coated over amore sensitive emulsion, a higher contrast is realized than when the twoemulsions are blended. It is preferred that the most sensitive emulsionbe located nearest the source of exposing radiation and the slowestemulsion be located nearest the support.

One or more of the layer units of the photothermographic element ispreferably subdivided into at least two, and more preferably three ormore sub-unit layers. It is preferred that all light sensitive silverhalide emulsions in the color recording unit have spectral sensitivityin the same region of the visible spectrum. In this embodiment, whileall silver halide emulsions incorporated in the unit have spectralabsorptances according to invention, it is expected that there are minordifferences in spectral absorptance properties between them. In stillmore preferred embodiments, the sensitizations of the slower silverhalide emulsions are specifically tailored to account for the lightshielding effects of the faster silver halide emulsions of the layerunit that reside above them, in order to provide an imagewise uniformspectral response by the photographic recording material as exposurevaries with low to high light levels. Thus higher proportions of peaklight absorbing spectral sensitizing dyes may be desirable in the sloweremulsions of the subdivided layer unit to account for on-peak shieldingand broadening of the underlying layer spectral sensitivity.

The photothermographic element may have interlayers that are hydrophiliccolloid layers having as their primary function color contaminationreduction-i.e., prevention of oxidized developing agent from migratingto an adjacent recording layer unit before reacting with dye-formingcoupler. The interlayers are in part effective simply by increasing thediffusion path length that oxidized developing agent must travel. Toincrease the effectiveness of the interlayers to intercept oxidizeddeveloping agent, it is conventional practice to incorporate a reducingagent capable of reacting with oxidized developing agent. Antistainagents (oxidized developing agent scavengers) can be selected from amongthose disclosed by Research Disclosure I, X. Dye image formers andmodifiers, D. Hue modifiers/stabilization, paragraph (2).

The yellow filter dye compositions, for use in IL1, of the presentinvention are particularly useful when one or more silver halideemulsions in GU and RU are high bromide emulsions and, hence havesignificant native sensitivity to blue light.

A photothermographic element may comprise a surface overcoat SOC whichis a hydrophilic colloid layer that is provided for physical protectionof the color negative elements during handling and processing. Each SOCalso provides a convenient location for incorporation of addenda thatare most effective at or near the surface of the color negative element.In some instances the surface overcoat is divided into a surface layerand an interlayer, the latter functioning as spacer between the addendain the surface layer and the adjacent recording layer unit. In anothercommon variant form, addenda are distributed between the surface layerand the interlayer, with the latter containing addenda that arecompatible with the adjacent recording layer unit. Most typically theSOC contains addenda, such as coating aids, plasticizers and lubricants,antistats and matting agents, such as illustrated by Research DisclosureI, Section IX. Coating physical property modifying addenda. The SOCoverlying the emulsion layers additionally preferably contains anultraviolet absorber, such as illustrated by Research Disclosure I,Section VI. UV dyes/optical brighteners/luminescent dyes, paragraph (1).

Alternative layer units sequences can be employed and are particularlyattractive for some emulsion choices. Using high chloride emulsionsand/or thin (<0.2 μm mean grain thickness) tabular grain emulsions allpossible interchanges of the positions of BU, GU and RU can beundertaken without risk of blue light contamination of the minus bluerecords, since these emulsions exhibit negligible native sensitivity inthe visible spectrum. For the same reason, it is unnecessary toincorporate blue light absorbers in the interlayers.

A number of modifications of color negative elements have been suggestedfor accommodating scanning, as illustrated by Research Disclosure I,Section XIV. Scan facilitating features. These systems to the extentcompatible with the color negative element constructions described aboveare contemplated for use in the practice of this invention.

It is also contemplated that the imaging element of this invention maybe used with non-conventional sensitization schemes. For example,instead of using imaging layers sensitized to the red, green, and blueregions of the spectrum, the light-sensitive material may have onewhite-sensitive layer to record scene luminance, and two color-sensitivelayers to record scene chrominance. Following development, the resultingimage can be scanned and digitally reprocessed to reconstruct the fullcolors of the original scene as described in U.S. Pat. No. 5,962,205.The imaging element may also comprise a pan-sensitized emulsion withaccompanying color-separation exposure. In this embodiment, thedevelopers of the invention would give rise to a colored or neutralimage which, in conjunction with the separation exposure, would enablefull recovery of the original scene color values. In such an element,the image may be formed by either developed silver density, acombination of one or more conventional couplers, or “black” couplerssuch as resorcinol couplers. The separation exposure may be made eithersequentially through appropriate filters, or simultaneously through asystem of spatially discreet filter elements (commonly called a “colorfilter array”).

The imaging element of the invention may also be a black and whiteimage-forming material comprised, for example, of a pan-sensitizedsilver halide emulsion and a developer of the invention. In thisembodiment, the image may be formed by developed silver densityfollowing processing, or by a coupler that generates a dye which can beused to carry the neutral image tone scale.

The photothermographic elements of the present invention are preferablyof type B as disclosed in Research Disclosure I. Type B elements containin reactive association a photosensitive silver halide, a reducing agentor developer, optionally an activator, a coating vehicle or binder, anda salt or complex of an organic compound with silver ion. In thesesystems, this organic complex is reduced during development to yieldsilver metal. The organic silver salt will be referred to as the silverdonor. References describing such imaging elements include, for example,U.S. Pat. Nos. 3,457,075; 4,459,350; 4,264,725 and 4,741,992. In thetype B photothermographic material it is believed that the latent imagesilver from the silver halide acts as a catalyst for the describedimage-forming combination upon processing. In these systems, a preferredconcentration of photographic silver halide is within the range of 0.01to 100 moles of photographic silver halide per mole of silver donor inthe photothermographic material.

The Type B photothermographic element comprises an oxidation-reductionimage forming combination that contains an organic silver salt oxidizingagent. The organic silver salt is a silver salt which is comparativelystable to light, but aids in the formation of a silver image when heatedto 80° C. or higher in the presence of an exposed photocatalyst (i.e.,the photosensitive silver halide) and a reducing agent.

Suitable organic silver salts include silver salts of organic compounds.Especially in the case of black and white or monochromicphotothermographic films, preferred examples thereof include compoundshaving a carboxyl group, for example, a silver salt of an aliphaticcarboxylic acid or a silver salt of an aromatic carboxylic acid.Preferred examples of the silver salts of aliphatic carboxylic acidsinclude silver behenate, silver stearate, silver oleate, silverlaureate, silver caprate, silver myristate, silver palmitate, silvermaleate, silver fumarate, silver tartarate, silver furoate, silverlinoleate, silver butyrate and silver camphorate, mixtures thereof, etc.Silver salts which are substitutable with a halogen atom or a hydroxylgroup can also be effectively used. Preferred examples of the silversalts of aromatic carboxylic acid and other carboxyl group-containingcompounds include silver benzoate, a silver-substituted benzoate such assilver 3,5-dihydroxybenzoate, silver o-methylbenzoate, silverm-methylbenzoate, silver p-methylbenzoate, silver 2,4-dichlorobenzoate,silver acetamidobenzoate, silver p-phenylbenzoate, etc., silver gallate,silver tannate, silver phthalate, silver terephthalate, silversalicylate, silver phenylacetate, silver pyromellilate, a silver salt of3-carboxymethyl-4-methyl-4-thiazoline-2-thione or the like as describedin U.S. Pat. No. 3,785,830, and silver salt of an aliphatic carboxylicacid containing a thioether group as described in U.S. Pat. No.3,330,663.

Preferred examples of organic silver donors for color photothermographyinclude silver salts of benzotriazole and derivative thereof asdescribed in Japanese patent publications 30270/69 and 18146/70, forexample a silver salt of benzotriazole or methylbenzotriazole, etc., asilver salt of a halogen substituted benzotriazole, such as a silversalt of 5-chlorobenzotriazole, etc., a silver salt of 1,2,4-triazole, asilver salt of 3-amino-5-mercaptobenzyl-1,2,4-triazole, of 1H-tetrazoleas described in U.S. Pat. No. 4,220,709, a silver salt of imidazole andan imidazole derivative, and the like.

The photosensitive silver halide grains and the organic silver salt arecoated so that they are in catalytic proximity during development. Theycan be coated in contiguous layers, but are preferably mixed prior tocoating. Conventional mixing techniques are illustrated by ResearchDisclosure, Item 17029, cited above, as well as U.S. Pat. No. 3,700,458and published Japanese patent applications Nos. 32928/75, 13224/74,17216/75 and 42729/76.

Any convenient selection from among conventional radiation-sensitivesilver halide emulsions can be incorporated within the layer units andused to provide the spectral absorptances of the invention. Mostcommonly high bromide emulsions containing a minor amount of iodide areemployed. To realize higher rates of processing, high chloride emulsionscan be employed. Radiation-sensitive silver chloride, silver bromide,silver iodobromide, silver iodochloride, silver chlorobromide, silverbromochloride, silver iodochlorobromide and silver iodobromochloridegrains are all contemplated. The grains can be either regular orirregular (e.g., tabular). Illustrations of conventionalradiation-sensitive silver halide emulsions are provided by ResearchDisclosure I, cited above, I. Emulsion grains and their preparation.Chemical sensitization of the emulsions, which can take any conventionalform, is illustrated in section IV. Chemical sensitization. The emulsionlayers also typically include one or more antifoggants or stabilizers,which can take any conventional form, as illustrated by section VII.Antifoggants and stabilizers.

The silver halide grains to be used in a photothermographic element maybe prepared according to methods known in the art, such as thosedescribed in Research Disclosure I, cited above, and James, The Theoryof the Photographic Process. These include methods such as ammoniacalemulsion making, neutral or acidic emulsion making, and others known inthe art. These methods generally involve mixing a water soluble silversalt with a water soluble halide salt in the presence of a protectivecolloid, and controlling the temperature, pAg, pH values, etc, atsuitable values during formation of the silver halide by precipitation.In the course of grain precipitation one or more dopants (grainocclusions other than silver and halide) can be introduced to modifygrain properties.

In a photothermographic element, the silver halide is typically providedin the form of an emulsion, including a vehicle for coating the emulsionas a layer of the element. Useful vehicles include both naturallyoccurring substances such as proteins, protein derivatives, cellulosederivatives (e.g., cellulose esters, ethers, and both anionically andcationically substituted cellulosics), gelatin (e.g., alkali-treatedgelatin such as cattle bone or hide gelatin, or acid treated gelatinsuch as pigskin gelatin), deionized gelatin, gelatin derivatives (e.g.,acetylated gelatin, phthalated gelatin, and the like), and others asdescribed in Research Disclosure, I. Also useful as vehicles or vehicleextenders are hydrophilic water-permeable colloids. These includesynthetic polymeric peptizers, carriers, and/or binders such aspoly(vinyl alcohol), poly(vinyl lactams), acrylamide polymers, polyvinylacetals, polymers of alkyl and sulfoalkyl acrylates and methacrylates,hydrolyzed polyvinyl acetates, polyamides, polyvinyl pyridine,methacrylamide copolymers. The vehicle can be present in the emulsion inany amount useful in photographic emulsions. The emulsion can alsoinclude any of the addenda known to be useful in photographic emulsions.

While any useful quantity of light sensitive silver, as silver halide,can be employed in the elements useful in this invention, it ispreferred that the total quantity be less than 10 g/m² of silver. Silverquantities of less than 7 g/m² are preferred, and silver quantities ofless than 5 g/m² are even more preferred. The lower quantities of silverimprove the optics of the elements, thus enabling the production ofsharper pictures using the elements.

Because in one embodiment of the invention only silver development isrequired, color developers (p-phenylene diamines or p-aminophenolics)are not obligatory. Other developers that are capable of forming asilver image may also be used, without regard to their ability to form acolored dye. Such developers include, in addition to p-phenylene diaminedevelopers and substituted p-aminophenols (3,5-dichloroaminophenol and3,5-dibromoaminophenol are particularly preferred choices) but alsop-sulfonamidophenols, ascorbic acid, low valent metal compounds,particularly those containing Fe(II), Cu(I), Co(II), Mn(II), V(II), orTi(III), hydrazine derivatives, hydroxylamine derivatives, phenidones.For incorporated developers, thermally unblocking blocked developers arepreferred.

In some cases, a development activator, also known as an alkali-releaseagent, base-release agent or an activator precursor can be useful in thedescribed photothermographic element of the invention. A developmentactivator, as described herein, is intended to mean an agent or acompound which aids the developing agent at processing temperatures todevelop a latent image in the imaging material. Useful developmentactivators or activator precursors are described, for example, inBelgian Pat. No. 709,967 published Feb. 29, 1968, and ResearchDisclosure, Volume 155, March 1977, Item 15567, published by IndustrialOpportunities Ltd., Homewell, Havant, Hampshire, PO9 1EF, UK. Examplesof useful activator precursors include guanidinium compounds such asguanidinium trichloroacetate, diguanidinium glutarate, succinate,malonate and the like; quaternary ammonium malonates; amino acids, suchas 6-aminocaproic acid and glycine; and 2-carboxycarboxamide activatorprecursors.

Examples of blocked developers that can be used in photographic elementsof the present invention include, but are not limited to, the blockeddeveloping agents described in U.S. Pat. No. 3,342,599, to Reeves;Research Disclosure (129 (1975) pp. 27–30) published by Kenneth MasonPublications, Ltd., Dudley Annex, 12a North Street, Emsworth, HampshireP010 7DQ, ENGLAND; U.S. Pat. No. 4,157,915, to Hamaoka et al.; U.S. Pat.No. 4,060,418, to Waxman and Mourning; and in U.S. Pat. No. 5,019,492.Particularly useful are those blocked developers described in U.S.application Ser. No. 09/476,234, filed Dec. 30, 1999, IMAGING ELEMENTCONTAINING A BLOCKED PHOTOGRAPICALLY USEFUL COMPOUND; U.S. applicationSer. No. 09/475,691, filed Dec. 30, 1999, IMAGING ELEMENT CONTAINING ABLOCKED PHOTOGRAPHICALLY USEFUL COMPOUND; U.S. application Ser. No.09/475,703, filed Dec. 30, 1999, IMAGING ELEMENT CONTAINING A BLOCKEDPHOTOGRAPHICALLY USEFUL COMPOUND; U.S. application Ser. No. 09/475,690,filed Dec. 30, 1999, IMAGING ELEMENT CONTAINING A BLOCKEDPHOTOGRAPHICALLY USEFUL COMPOUND; and U.S. application Ser. No.09/476,233, filed Dec. 30, 1999, PHOTOGRAPHIC OR PHOTOTHERMOGRAPHICELEMENT CONTAINING A BLOCKED PHOTOGRAPHICALLY USEFUL COMPOUND.

In one embodiment of the invention, the blocked developer is preferablyincorporated in one or more of the imaging layers of the imagingelement. The amount of blocked developer used is preferably 0.01 to 5g/m², more preferably 0.1 to 2 g/m² and most preferably 0.3 to 2 g/m² ineach layer to which it is added. These may be color forming or non-colorforming layers of the element. The blocked developer can be contained ina separate element that is contacted to the photographic element duringprocessing.

After image-wise exposure of the imaging element, the blocked developercan be activated during processing of the imaging element by thepresence of acid or base in the processing solution, by heating theimaging element during processing of the imaging element, and/or byplacing the imaging element in contact with a separate element, such asa laminate sheet, during processing. The laminate sheet optionallycontains additional processing chemicals such as those disclosed inSections XIX and XX of Research Disclosure, September 1996, Number 389,Item 38957 (hereafter referred to as (“Research Disclosure I”). Allsections referred to herein are sections of Research Disclosure I,unless otherwise indicated. Such chemicals include, for example,sulfites, hydroxylamine, hydroxamic acids and the like, antifoggants,such as alkali metal halides, nitrogen containing heterocycliccompounds, and the like, sequestering agents such as an organic acids,and other additives such as buffering agents, sulfonated polystyrene,stain reducing agents, biocides, desilvering agents, stabilizers and thelike.

It is useful to include a melt-forming compound in a photothermographicelement, such as in the imaging layers and in the antihalation layer orfilter layer, as described. Combinations of melt-forming compounds ormelt-formers can also be useful if desired. The term “melt-formingcompound” as employed herein is intended to mean a compound which uponheating to the described processing temperature provides an improvedreaction medium, typically a molten medium, wherein the describedreaction combination can provide a better image. The exact nature of thereaction medium at processing temperatures described is not fullyunderstood; however, it is believed that at reaction temperatures a meltoccurs which permits the reaction components to better interact. Usefulmelt-forming compounds are typically separate components from thereaction combination, although the reaction combination can enter intothe melt formation. Typically useful melt-forming compounds are amides,imides, cyclic ureas and triazoles which are compatible with other ofthe components of the materials of the invention. Useful melt-formingcompounds are described, for example, in Research Disclosure, Vol. 150,October 1976, Item 15049 of LaRossa and Boettcher, published byIndustrial Opportunities Ltd., Homewell, Havant, Hampshire, PO9 1EF, UK.As described, the filter layers of the invention can comprise amelt-forming compound if desired. A preferred melt-former issalicylanilide and similar compounds. Examples of melt formers orthermal solvents are, for example, salicylanilide, phthalimide,N-hydroxyphthalimide, N-potassium-phthalimide, succinimide,N-hydroxy-1,8-naphthalimide, phthalazine, 1-(2H)-phthalazinone,2-acetylphthalazinone, benzanilide, and benzenesulfonamide. Prior-artbase precursors are disclosed, for example, in U.S. Pat. No. 6,013,420to Windender. Examples of toning agents and toning agent combinationsare described in, for example, Research Disclosure, June 1978, Item No.17029 and U.S. Pat. No. 4,123,282.

A range of concentration of melt-forming compound or melt-formingcompound combination is useful in the heat developable photographicmaterials described. The optimum concentration of melt-forming compoundwill depend upon such factors as the particular imaging material,desired image, processing conditions and the like.

The photothermographic elements according to the invention can containan

Photothermographic elements as described can contain addenda that areknown to aid in formation of a useful image. The photothermographicelement can contain development modifiers that function as speedincreasing compounds, sensitizing dyes, hardeners, anti-static agents,plasticizers and lubricants, coating aids, brighteners, absorbing andfilter dyes, such as described in Research Disclosure, December 1978,Item No. 17643 and Research Disclosure, June 1978, Item No. 17029.

The layers of the photothermographic element are coated on a support bycoating procedures known in the photographic art, including dip coating,air knife coating, curtain coating or extrusion coating using hoppers.If desired, two or more layers are coated simultaneously.

A photothermographic element as described preferably comprises a thermalstabilizer to help stabilize the photothermographic element prior toexposure and processing. Such a thermal stabilizer provides improvedstability of the photothermographic element during storage. Preferredthermal stabilizers are 2-bromo-2-arylsulfonylacetamides, such as2-bromo-2-p-tolysulfonylacetamide; 2-(tribromomethylsulfonyl)benzothiazole; and6-substituted-2,4-bis(tribromomethyl)-s-triazines, such as 6-methyl or6-phenyl-2,4-bis(tribromomethyl)-s-triazine.

Photographic elements of the present invention are preferably imagewiseexposed using any of the known techniques, including those described inResearch Disclosure I, Section XVI. This typically involves exposure tolight in the visible region of the spectrum, and typically such exposureis of a live image through a lens, although exposure can also beexposure to a stored image (such as a computer stored image) by means oflight emitting devices (such as light emitting diodes, CRT and thelike). The photothermographic elements are also exposed by means ofvarious forms of energy, including ultraviolet and infrared regions ofthe electromagnetic spectrum as well as electron beam and betaradiation, gamma ray, x-ray, alpha particle, neutron radiation and otherforms of corpuscular wave-like radiant energy in either non-coherent(random phase) or coherent (in phase) forms produced by lasers.Exposures are monochromatic, orthochromatic, or panchromatic dependingupon the spectral sensitization of the photographic silver halide.Imagewise exposure is preferably for a time and intensity sufficient toproduce a developable latent image in the photothermographic element.

Once yellow, magenta, and cyan dye image records, or other combinationof three distinct colors, have been formed in the processed photographicelements of the invention, conventional techniques can be employed forretrieving the image information for each color record and manipulatingthe record for subsequent creation of a color balanced viewable image.For example, it is possible to scan the photographic elementsuccessively within the three distinct color regions of the spectrum orto incorporate blue, green, and red light within a single scanning beamthat is divided and passed through blue, green, and red filters to formseparate scanning beams for each color record. A simple technique is toscan the photographic element point-by-point along a series of laterallyoffset parallel scan paths. The intensity of light passing through theelement at a scanning point is noted by a sensor which convertsradiation received into an electrical signal. Most generally thiselectronic signal is further manipulated to form a useful electronicrecord of the image. For example, the electrical signal can be passedthrough an analog-to-digital converter and sent to a digital computertogether with location information required for pixel (point) locationwithin the image. In another embodiment, this electronic signal isencoded with calorimetric or tonal information to form an electronicrecord that is suitable to allow reconstruction of the image intoviewable forms such as computer monitor displayed images, televisionimages, printed images, and so forth.

In one embodiment, a photothermographic elements can be scanned prior toany removal of silver halide from the element. The remaining silverhalide yields a turbid coating, and it is found that improved scannedimage quality for such a system can be obtained by the use of scannersthat employ diffuse illumination optics. Any technique known in the artfor producing diffuse illumination can be used. Preferred systemsinclude reflective systems, that employ a diffusing cavity whoseinterior walls are specifically designed to produce a high degree ofdiffuse reflection, and transmissive systems, where diffusion of a beamof specular light is accomplished by the use of an optical elementplaced in the beam that serves to scatter light. Such elements can beeither glass or plastic that either incorporate a component thatproduces the desired scattering, or have been given a surface treatmentto promote the desired scattering.

In view of advances in the art of scanning technologies, it has nowbecome natural and practical for photothermographic color films such asdisclosed in EP 0762 201 to be scanned, which can be accomplishedwithout the necessity of removing the silver or silver-halide from thenegative, although special arrangements for such scanning can be made toimprove its quality. See, for example, Simmons U.S. Pat. No. 5,391,443.Method for the scanning of such films are also disclosed in commonlyassigned U.S. Ser. No. 60/211,364 and U.S. Ser. No. 60/211,061, herebyincorporated by reference in their entirety.

For example, it is possible to scan the photographic elementsuccessively within the blue, green, and red regions of the spectrum orto incorporate blue, green, and red light within a single scanning beamthat is divided and passed through blue, green, and red filters to formseparate scanning beams for each color record. If other colors areimagewise present in the element, then appropriately colored light beamsare employed. A simple technique is to scan the photographic elementpoint-by-point along a series of laterally offset parallel scan paths. Asensor that converts radiation received into an electrical signal notesthe intensity of light passing through the element at a scanning point.Most generally this electronic signal is further manipulated to form auseful electronic record of the image. For example, the electricalsignal can be passed through an analog-to-digital converter and sent toa digital computer together with location information required for pixel(point) location within the image. The number of pixels collected inthis manner can be varied as dictated by the desired image quality.

The electronic signal can form an electronic record that is suitable toallow reconstruction of the image into viewable forms such as computermonitor displayed images, television images, optically, mechanically ordigitally printed images and displays and so forth all as known in theart. The formed image can be stored or transmitted to enable furthermanipulation or viewing, such as in U.S. Ser. No. 09/592,816 titled ANIMAGE PROCESSING AND MANIPULATION SYSTEM to Richard P. Szajewski, AlanSowinski and John Buhr.

Illustrative systems of scan signal manipulation, including techniquesfor maximizing the quality of image records, are disclosed by Bayer U.S.Pat. No. 4,553,156; Urabe et al U.S. Pat. No. 4,591,923; Sasaki et alU.S. Pat. No. 4,631,578; Alkofer U.S. Pat. No. 4,654,722; Yamada et alU.S. Pat. No. 4,670,793; Klees U.S. Pat. Nos. 4,694,342 and 4,962,542;Powell U.S. Pat. No. 4,805,031; Mayne et al U.S. Pat. No. 4,829,370;Abdulwahab U.S. Pat. No. 4,839,721; Matsunawa et al U.S. Pat. Nos.4,841,361 and 4,937,662; Mizukoshi et al U.S. Pat. No. 4,891,713;Petilli U.S. Pat. No. 4,912,569; Sullivan et al U.S. Pat. Nos. 4,920,501and 5,070,413; Kimoto et al U.S. Pat. No. 4,929,979; Hirosawa et al U.S.Pat. No. 4,972,256; Kaplan U.S. Pat. No. 4,977,521; Sakai U.S. Pat. No.4,979,027; Ng U.S. Pat. No. 5,003,494; Katayama et al U.S. Pat. No.5,008,950; Kimura et al U.S. Pat. No. 5,065,255; Osamu et al U.S. Pat.No. 5,051,842; Lee et al U.S. Pat. No. 5,012,333; Bowers et al U.S. Pat.No. 5,107,346; Telle U.S. Pat. No. 5,105,266; MacDonald et al U.S. Pat.No. 5,105,469; and Kwon et al U.S. Pat. No. 5,081,692. Techniques forcolor balance adjustments during scanning are disclosed by Moore et alU.S. Pat. No. 5,049,984 and Davis U.S. Pat. No. 5,541,645.

The digital color records once acquired are in most instances adjustedto produce a pleasingly color balanced image for viewing and to preservethe color fidelity of the image bearing signals through varioustransformations or renderings for outputting, either on a video monitoror when printed as a conventional color print. Preferred techniques fortransforming image bearing signals after scanning are disclosed byGiorgianni et al U.S. Pat. No. 5,267,030, the disclosures of which areherein incorporated by reference. Further illustrations of thecapability of those skilled in the art to manage color digital imageinformation are provided by Giorgianni and Madden Digital ColorManagement, Addison-Wesley, 1998.

For illustrative purposes, a non-exhaustive list of photothermographicfilm processes involving a common dry heat development step are asfollows:

1. heat development=>scan=>stabilize (for example, with alaminate)=>scan=>obtain returnable archival film.

2. heat development=>fix bath=>water wash=>dry=>scan=>obtain returnablearchival film

3. heat development=>scan=>blix bath=>dry=>scan=>recycle all or part ofthe silver in film

4. heat development=>bleach laminate=>fix laminate=>scan=>(recycle allor part of the silver in film)

5. heat development=>bleach=>wash=>fix=>wash=>dry=>relatively slow, highquality scan

In a preferred embodiment of a photothermographic film according to thepresent invention, the processing time to first image (either hard orsoft display for customer/consumer viewing), including (i) thermaldevelopment of a film, (ii) scanning, and (iii) the formation of thepositive image from the developed film, is suitably less than 5 minutes,preferably less than 3.5 minutes, more preferably less than 2 minutes,most preferably less than about 1 minute. In one embodiment, such filmmight be amenable to development at kiosks, with the use of simple dryor apparently dry equipment. Thus, it is envisioned that a consumercould bring an imagewise exposed photographic film, for development andprinting, to a kiosk located at any one of a number of diverselocations, optionally independent from a wet-development lab, where thefilm could be developed and printed without any manipulation bythird-party technicians. A photothermographic color film, in which asilver-halide-containing color photographic element after imagewiseexposure can be developed merely by the external application of heatand/or relatively small amounts of alkaline or acidic water, but whichsame film is also amenable to development in an automated kiosk,preferably not requiring third-party manipulation, would havesignificant advantages. Assuming the availability and accessibility ofsuch kiosks, such photothermographic films could potentially bedeveloped at any time of day, “on demand,” in a matter minutes, withoutrequiring the participation of third-party processors, multiple-tankequipment and the like. Optional, such photographic processing couldpotentially be done on an “as needed” basis, even one roll at a time,without necessitating the high-volume processing that would justify, ina commercial setting, equipment capable of high-throughput. Colordevelopment and subsequent scanning of such a film could readily occuron an individual consumer basis, with the option of generating a displayelement corresponding to the developed color image. By kiosk is meant anautomated free-standing machine, self-contained and (in exchange forcertain payments) capable of developing a roll of imagewise exposed filmon a roll-by-roll basis, without the intervention of technicians orother third-party persons such as necessary in wet-chemicallaboratories. Typically, the customer will initiate and control thecarrying out of film processing and optional printing by means of acomputer interface. Such kiosks typically will be less than 6 cubicmeters in dimension, preferably 3 cubic meters or less in dimension, andhence commercially transportable to diverse locations. Such kiosks mayoptionally comprise a heater for color development, a scanner fordigitally recording the color image, and a device for transferring thecolor image to a display element.

The following examples are presented to illustrate the practice of thisinvention, but are not meant to limit it in any way. All percentages areby weight unless otherwise indicated.

EXAMPLES

The arylsulfonylacetic acid portion of BP-1 base precursor was preparedby reacting the corresponding amine (preparation described in U.S. Pat.No. 6,242,155 B1) with phthalic anhydride in glacial acetic acid in thepresence of triethylamine.

4-Phthalimido-phenylsulfonylacetic acid:

The compound 4-amino-phenylsulfonylacetic acid hemisulfate salt(preparation described in U.S. Pat. No. 6,242,155 B1) (104.4 g, 0.33mol) and phthalic anhydride (49.3 g, 0.33 mol) were combined in a 2liter 3-neck round bottom flask, fitted with a mechanical stirrer, athermometer and a condenser. Glacial acetic acid (1 L) was added to themixture. Triethylamine (7.4 g, 10.1 mol) was slowly added to thissuspension while being stirred at room temperature. The resultingmixture was heated to 110° C. for 3 hours, resulting in a clearsolution. It was then cooled to 50° C. and ice and water were added toit—resulting in the precipitation of white solid. Kept in therefrigerator overnight. Solid was filtered, washed with water and withligroin. It was then dried in the oven to give 56.8 g (yield 50%) of thedesired 4-phthalimido-phenylsulfonylacetic acid, 97% pure by HPLC.

The base precursors of the present invention were prepared using thegeneral procedures described in EP708086 A1 and U.S. Pat. No. 4,981,965.

Photographic Example

The following components are used in the example.

Silver Salt Dispersion SS-1:

A stirred reaction vessel was charged with 431 g of lime processedgelatin and 6569 g of distilled water. A solution containing 214 g ofbenzotriazole, 2150 g of distilled water, and 790 g of 2.5 molar sodiumhydroxide was prepared (Solution B). The mixture in the reaction vesselwas adjusted to a pAg of 7.25 and a pH of 8.00 by additions of SolutionB, nitric acid, and sodium hydroxide as needed.

A 4 l solution of 0.54 molar silver nitrate was added to the kettle at250 cc/minute, and the pAg was maintained at 7.25 by a simultaneousaddition of solution B. This process was continued until the silvernitrate solution was exhausted, at which point the mixture wasconcentrated by ultrafiltration. The resulting silver salt dispersioncontained fine particles of silver benzotriazole (AgBZT).

Silver Salt Dispersion SS-2:

A stirred reaction vessel was charged with 431 g of lime processedgelatin and 6569 g of distilled water. A solution containing 320 g of1-phenyl-5-mercaptotetrazole, 2044 g of distilled water, and 790 g of2.5 molar sodium hydroxide was prepared (Solution B). The mixture in thereaction vessel was adjusted to a pAg of 7.25 and a pH of 8.00 byadditions of Solution B, nitric acid, and sodium hydroxide as needed.

A 4 l solution of 0.54 molar silver nitrate was added to the kettle at250 cc/minute, and the pAg was maintained at 7.25 by a simultaneousaddition of solution B. This process was continued until the silvernitrate solution was exhausted, at which point the mixture wasconcentrated by ultrafiltration. The resulting silver salt dispersioncontained fine particles of the silver salt of1-phenyl-5-mercaptotetrazole (AgPMT).

Silver Halide Emulsions:

The emulsions employed in these examples are silver iodobromide tabulargrains precipitated by conventional means as known in the art. Themagenta and cyan imaging layers use the same silver halide precipitationwhich yields a 1.31 μm ECD by 0.121 μm thick emulsion containing 3.7%iodide. Both emulsions have been given chemical sensitizations as knownin the art to produce optimum sensitivity. The emulsion in the magentalayer is dyed with a mixture of dyes SM-1 and SM-2 in order to impartgreen light sensitivity (Emulsion EM-1), while the emulsion used in thecyan record is dyed with a mixture of dyes SC-1 and SC-2 in order toimpart red light sensitivity (Emulsion EC-1).

Coupler Dispersion CDM-1:

An oil based coupler dispersion was prepared by conventional meanscontaining coupler M-1, tricresyl phosphate, and2-butoxy-N,N-dibutyl-5-(1,1,3,3-tetramethylbutyl)-Benzenamine, at aweight ratio of 1:0.8:0.2.

Coupler Dispersion CDC-1:

A coupler dispersion was prepared by conventional means containingcoupler C-1 and dibutyl sebacate in a ratio of 1:1 solvents.

Antifoggant Dispersion AD-1:

A dispersion of the antifoggant AF-1 was prepared by conventional meanscontaining antifoggant AF-1 and the solvent N,N-dibutyldodecanamide inthe ratio of 1:2.

Melt Former MF-1 Dispersion (Salicylanilide):

A dispersion of salicylanilide was prepared by the method of ballmilling. To a total 20 g sample was added 3.0 gm salicylanilide solid,0.20 g polyvinyl pyrrolidone, 0.20 g Triton X 200 surfactant, 1.0 ggelatin, 15.6 g distilled water, and 20 mL of zirconia beads. The slurrywas ball milled for 48 hours. Following milling, the zirconia beads wereremoved by filtration. The slurry was refrigerated prior to use.

For preparations on a larger scale, the salicylanilide was media-milledto give a final dispersion containing 30% Salicylanilide, with 4% TritonX 200 surfactant and 4% polyvinyl pyrrolidone added relative to theweight of Salicylanilide. In some cases the dispersion was diluted withwater to 25% Salicylanilide or gelatin (5% of total) was added and theconcentration of Salicylanilide adjusted to 25%. Biocide may also beadded.

Blocked Developer BD-1 Dispersion:

The check dispersion was prepared by combining 3 g of BD-1 with 3 g of a10% Olin 10G aqueous solution, 9 g of high purity water and 15 ml of 0.7mm zirconium silicate beads. The mixture was milled for 90 minutes in ahigh-energy media mill. After milling, the dispersion was separated fromthe beads and diluted to 15% developer with high purity water. Thedispersion was examined by optical microscopy immediately after milling,and after being held for 24 hours at 45° C.

Base Precursor Dispersions:

The base precursor dispersions were prepared by the method of ballmilling.

The comparative base Precursor BP-C dispersion was prepared followingthe procedure below:

-   -   The following ingredients were combined in a 4-oz glass jar: 1.2        g of BP-C, 0.6 g of a 10% solution of the surfactant OLIN 10G in        water, 1.2 g of a 10% solution of polyvinylpyrrolidone in water,        21.0 g of high purity water, and 60 mL 1.8 mm zirconium oxide        ceramic beads. The jar was sealed and rolled at 65 ft/min for 3        days. Following milling, the zirconium oxide beads were removed        by filtration without dilution.

The dispersion of the base precursor BP-1, in accordance with thepresent invention, was prepared following the procedure below:

-   -   The following ingredients were combined in a 4-oz glass jar:        0.84 g of BP-1, 1.26 g of a 10% solution of the polymeric        surfactant Dapryl, 21.9 g of high purity water, and 60 mL 1.8 mm        zirconium oxide ceramic beads. The jar was sealed and rolled at        65 ft/min for 3 days. Following milling, the zirconium oxide        beads were removed by filtration without dilution.

The base precursors exhibited the following properties.

Onset Temperature of Solubility in CO₂ loss by TGA water @40° C.Analysis ID g/100 mL ° C. BP-C 0.22 127 Comparative BP-1 0.06 144invention UV-1

M-1

AF-1

C-1

BD-C

BP-C

BP-1

SM-1

SM-2

SC-1

SC-2

H-1

BYD-1

The above chemical components were incorporated into the followingcoating structure. All coatings were prepared on a 4.7 mil thickpoly(ethylene terephthalate) support. Variations to the coating weremade by adding base precursors to the Filter dye layer.

Laydown, Layer Component g/m² Overcoat Gelatin 1.076 Hardener H-1 0.247Silicone Lubricant 0.039 Polymeric Matte Beads 0.113 UV Absorber DyeUV-1 0.097 Magenta Imaging Layer Gelatin 4.304 AG-BZT (from SS-1) 0.323AG-PMT (from SS-2) 0.323 Coupler M-1 (from CDM-1) 0.538 Antifoggant AF-10.022 Melt Former MF-1 0.861 Blocked Developer BD-1 0.861 Emulsion EM-10.861 Filter Dye Layer Gelatin 1.076 Bleachable Yellow Dye BYD-1 0.215Cyan Imaging Layer Gelatin 4.304 AG-BZT (from SS-1) 0.323 AG-PMT (fromSS-2) 0.323 Coupler C-1 (from CDC-1) 0.538 Antifoggant AF-1 0.022 MeltFormer MF-1 0.861 Blocked Developer BD-1 0.861 Emulsion EC-1 0.861Undercoat Gelatin 1.614

The resulting coatings were exposed through a step wedge to a 3.04 loglux light source at 3000K filtered by Daylight 5A and Wratten 2Bfilters. The exposure time was 0.01 second. After exposure, the coatingwas thermally processed by contact with a heated drum for 18 seconds.The drum was maintained at a temperature of 157.5° C. After processing,the coatings were evaluated for Dmin and for the presence of pinholes.The pinholes represent areas where escaping carbon dioxide gas damagesthe coating and leaves microscopic areas of density lower than thesurrounding areas.

The Following coatings were created in which the base precursor wasplaced in the filter dye layer at a level of 1.30 g/m2.

Base Coating Precursor Cyan Dmin Magenta Dmin Pinholes C-1 None 0.1960.266 No C-2 BP-C 1.16 0.931 Yes C-3 BP-1 0.196 0.248 No

As shown by the above table, the comparative base precursor BP-C led notonly to significant Dmin growth in both magenta and cyan records, butalso to the presence of pinholes. Image analysis showed severe pinholeformation resulting in approximately 3800 pinholes per square centimeterin the processed coating. The inventive base precursor BP-1, on theother hand, showed no Dmin signal within experimental error, as well asno pinhole formation.

The invention has been described in detail with particular reference tocertain preferred embodiments thereof, but it will be understood thatvariations and modifications can be effected within the spirit and scopeof the invention.

1. A photothermographic element comprising a support having thereon atleast one coatable light-sensitive imaging layer and at least one layercomprising a base precursor comprising an organic base, and with anarylsulfonylacetic acid having the following structure:

wherein each of R² and R³ is a monovalent group selected from the groupconsisting of hydrogen, an alkyl group, an alkenyl group, a cycloalkylgroup, an aralkyl group, an aryl group and a heterocyclic group, whereineach of the monovalent groups may have one or more substituent groups;the subscript n is 1 to 4 and each of the R¹ groups may be independentlyselected from one or more substituent groups and wherein said organicbase comprises two to four guanidine moieties.
 2. The photothermographicelement of claim 1 wherein said base precursor is in bleachingassociation with a filter dye.
 3. The photothermographic element ofclaim 2 wherein said filter dye and said base precursor are both in acoatable light-absorbing layer.
 4. The photothermographic element ofclaim 1 wherein said base precursor is in association with one or moreblocked photographically useful compounds, and the base precursor iscapable of promoting the unblocking of said one or more blockedphotographically useful compounds.
 5. The photothermographic element ofclaim 2 wherein the dye is a barbituric acid arylidene filter dye. 6.The photothermographic element of claim 5 wherein the arylidene filterdye is represented by the following formula:

wherein A comprises an acidic nucleus, comprising a cyclic ketomethylenemoiety; D contains an aryl or heterocyclic moiety which may besubstituted or fused, and R represents hydrogen, an aryl groupcontaining 6 to 14 carbon atoms, or an alkyl group containing 1 to 12carbon atoms which groups may optionally be substituted.
 7. Thephotothermographic element of claim 6 wherein the A group is representedby the following structure:

wherein R¹ and R² each individually represent a hydrogen, an alkyl,aryl, aralkyl, heterocyclic or cycloalkyl group, which groups that canbe substituted or unsubstituted.
 8. The photothermographic element ofclaim 2 wherein the base precursor is capable of reacting with the dyeat a temperature higher than 80° C.
 9. The photothermographic element ofclaim 1 wherein the organic base is a diacidic to tetraacidic basehaving the following Structure:R¹³(—B)_(n) wherein R¹³ is an n-valent residue of a hydrocarbon orheterocyclic ring, each of which may have one or more substituentgroups; “n” is an integer of 2 to 4; and wherein “B” is a monovalentgroup corresponding to an atomic group formed by removing one hydrogenatom from a guanidine having the Structure:

 wherein each of R¹⁴, R¹⁵, R¹⁶, R¹⁷ and R¹⁸ are independently amonovalent group selected from the group consisting of hydrogen, analkyl group, an alkenyl group, an alkynyl group, a cycloalkyl group, anaralkyl group, an aryl group and a heterocyclic group, wherein each ofthe monovalent groups may have one or more substituent groups; or anytwo of R¹⁴, R¹⁵, R¹⁶, R¹⁷ and R¹⁸ may be combined together to form afive-membered or six-membered nitrogen containing heterocyclic ring. 10.The photothermographic element of claim 9 wherein each of R¹⁴, R¹⁵, R¹⁶,R¹⁷ and R¹⁸ is hydrogen or an alkyl group.
 11. The photothermographicelement of claim 9 wherein n is
 2. 12. The photothermographic element ofclaim 9 wherein R¹³ is an alkylene group or an arylene group, which mayhave one or more substituent groups.
 13. The photothermographic elementof claim 1 wherein the base precursor is a bisguanidine base precursor.14. The photothermographic element of claim 1 wherein the base precursoris a bisguanidinium salt of an arylsulfonylacetic acid having thefollowing formula:

wherein the subscript n is 1 to 4, wherein p is 2, 3 or 4; the groups R²and R³ are independently a hydrogen or a substituted or unsubstitutedalkyl or aryl group; and the group R¹ is independently selected fromhydrogen, an aryl, alkoxy, or an alkoxycarbonyl group.
 15. Thephotothermographic element of claim 1 comprising, on the support, atleast one light-sensitive silver halide emulsion layer and at least onelight-absorbing non-light sensitive layer comprising a filter dye. 16.The photothermographic element of claim 2 wherein said filter dye iscapable of becoming at least about 50% colorless within about 5 minutesupon heating to a temperature of at least about 90° C.
 17. Aphotothermographic element according to claim 1 wherein thephotothermographic element contains an imaging layer comprising ablocked developer, a light-sensitive silver halide emulsion, and anon-light sensitive silver salt oxidizing agent.
 18. Aphotothermographic element according to claim 1 comprising a mixture ofat least two organic silver salts, at least one of which is a non-lightsensitive silver salt oxidizing agent.
 19. The photothermographicelement of claim 1 comprising, on the support, at least threeaqueous-coatable light-sensitive imaging layers which have theirindividual sensitivities in different wavelength regions and also anaqueous-coatable filter layer, below the imaging layers, comprising atleast one antihalation dye in association with an effective amount, forbleaching of the antihalation dye, of the base precursor, wherein saidfilter dye becomes at least about 50% colorless within about 5 minutesupon heating to a temperature of at least about 90° C.
 20. Aphotothermographic process for preparing visible photographic imagescomprising the steps of: (a) providing a photothermographic element asin claim 1 comprising, coating on the support, (i) at least oneaqueous-coatable layer containing photosensitive silver halide, awater-insoluble organic silver salt as an oxidizing agent, a reducingagent for silver ion, and (ii) a aqueous-coatable light-absorbing layercomprising a filter dye in association with an effective amount, forbleaching of the filter dye, of the base precursor; and (b) thermallydeveloping the film step without any externally applied developingagent, comprising heating said film to an average temperature of atleast 90° C. for at least 0.5 seconds, wherein said filter dye becomesat least about 50% colorless.